1. Field of the Invention
The present invention relates to a sheet feeding apparatus for feeding sheets one by one and particularly with reducing double-feeding, and an image forming apparatus such as a copying machine, a printer, a facsimile and the like, having such a sheet feeding apparatus.
2. Related Background Art
In conventional sheet feeding apparatuses, a time period from when feeding of a sheet is started to when the sheet is detected by a detection means (for example, sheet feed sensor) for detecting the feeding of the sheet was constant. After start of the feeding of the sheet, if the sheet is not detected by the sheet feed sensor even after a predetermined time period is elapsed, it is assumed that sheet jam occurs, and the sheet jam is informed of an operator by an alarming means.
Cause of the sheet jam includes wear and/or looseness of a sheet feed roller or a sheet feed belt in a sheet feeding mechanism, paper powder adhered to the sheet and sheet slip due to feeding by low coefficient of friction.
Even when the sheet feeding abnormal condition is informed of the operator by the alarming means, the operator may perform the sheet feed control (retry) again to continue the operation of the sheet feeding apparatus.
Also in such a case, the sheet feeding apparatus repeats the same operation again. By repeating the same operation, for any reason, the abnormal condition may be disappeared to permit the feeding of the sheet.
However, if the sheet feeding apparatus repeats the same operation, the poor sheet feeding may often occur due to the same reason. In this case, the operator do not know how to cope with the poor sheet feeding. As a result, entire sheet feeding efficiency of the sheet feeding apparatus is worsened.
Further, in an image forming apparatus having such a sheet feeding apparatus, since the sheet is not fed from the sheet feeding apparatus smoothly, an image forming efficiency is worsened.